Apparatus



O. G. KAASA Nov. 1, 1955 APPARATUS Filed May l1, 1954 INVENTOR ORIN G.KAASA.

i( O {NEYS United States arent APPARATUS Orin G. Kaasa, Tulsa, Gkla.,assignor to Sinclair Oil and Gas Company, a corporation of MaineApplication May 11, 1954, Serial No. 429,669

1 Claim. (Cl. 16o-59) This invention relates to an apparatus forproducing high temperatures in subterranean passages by combustion ofoil. More particularly, this invention relates to a bottom hole heaterand burner which can be lowered into subterranean passages, such as oil,shale or water wells, and while in this position burn an oil streampassed from the earths surface to produce high temperatures in the wellswhich can be followed from the earths surface.

There have been proposed various methods for treating subterraneanpassages such as oil, shale and water wells to increase the amount ofvalues recovered from the earth, whic-h methods include initiation andmaintenance of combustion of fuels in the passages at or near the pointof heat application. I have now devised an apparatus for establishing ahighly heated zone at controlled temperatures in these subterraneanpassages that is simple in construction, relatively simple to operateand economical and that provides adequate means for followingtemperatures of heating and combustion in the passages. My device isparticularly effective in providing a rapid, compact and inexpensivemeans for igniting oilbearing sands and in providing control of burningrate and passage temperature over extended periods of time. Ignition ofoil-bearing sands provides for increased oil recovery from the strata asliquids, vapors or gaseous decomposition production, e. g., products ofcombustion. Heated zones are also used in conjunction with smalldiameter cemented tubing which has been used for water injection andwhich has become sludged or clogged with foreign agents. These agentsmay consist of bacterial organisms, insoluble carbonates, or heavy waxyhydrocarbons, and are of such a nature that they are either consumed atthe point of clogging or disintegrated thereby to a powdery form by heator tire. After this treatment, they can be blown from the well by air orilushed to the surface by water.

My invention will be described more particularly with reference to theaccompanying drawing which is a crosssectional view of my bottom holeheater and burner which is suitable for the above and other purposes.

The burner comprises an elongated cylindrical hollow tubing member 2which is adapted at its upper end to be connected by coupling 3 to astring of hollow tubing 4 which is lowered into the subterraneanpassage. Tubing 2 is open at its lower end and has projecting from thisend a thermocouple 5 situated within a thermowell 6. The thermowell is ahollow cylindrical metallic tubing, e. g., stainless steel, having aclosed lower end which houses the thermocouple. The thermowell extendsupwardly into the tubing 2 and through its side at a substantialdistance from its lower end. At the point where the thermowell passesthrough the tubing 2, it is welded so that no liquid or gas can escapefrom the tubing. The upper end of the thermowell is either llush withthe outside surface of tubing 2 or, preferably, extends just beyondtubing 2 a distance small enough not to interfere with the lowering ofthe heater into the passage. The thermowell houses the electrical leadsleading to the ther- ICC mocouple, which leads extend to the earthssurface after passing through the top of the thermowell through tightseals. Alternatively, the thermowell could extend to the earths surfaceoutside of tubing 2 or by passage through tubing 4; however, in thelatter position, it would unnecessarily affect the flow of gas andliquids through the tubing string.

Since the tubing 2 is hollow and is connected to a tubing 4 leading tothe earths surface, oil or oil and air can be passed downwardly throughthe string of tubing 4 and tubing 2 of the burner. The thermowell 6 isof such diameter that its cross section occupies a substantial portionof the cross sectional area of the tubing 2, thus providing narrow butfree passages between the thermowell and tubing 2 for passage of the oiland air descending from the earths surface. Disposed around asubstantial lower portion of tubing 2 is heating wire 7 which haselectrical connecting leads 8 passing to the surface of the ground. Theheating wire is held out of contact with tubing 2 by insulating beads12. A protective sheath 9 is disposed around the heating coil 7 andencloses the coil in a chamber formed between it and tubing 2 by meetingthe tubing at points 10 and 11.

In operation, my bottom hole heater and burner is attached to the end ofa string of well tubing and lowered into the passage, e. g., an oilwell. As it is lowered the thermocouple leads and electrical coil leadsare extended so that their upper ends are at the earths surface. Theoutside diameter of the burner defined by the protective sheath is suchthat a space is left between it and the passage bore, its casing ortubing as the case may be. Thus the outside diameter of the protectivesheath must be smaller than the internal diameter of the structure intowhich it is being lowered to permit lowering and, possibly, passage ofair to help support combustion.

After appropriate surface connections and seals have been made, air orany oxygen-rich gas is introduced through or around the tubing string 4and burner tubing 2, and it passes the thermocouple situated in thelower end of the thermowell projecting beyond the burner tubing. As theair passes down the well it is heated by the electrical heating coilsurrounding the burner tubing. When the thermocouple indicates atemperature above about 500 F., oil is fed through the tubing 2 and theheating of both the oil and the air is continued until combustion isinitiated. As noted, the air to support cornbustion can pass inside oftubing 2 or outside of sheath 9 or can take both courses. Temperature ofthe burning is followed by noting at the earths surface the reaction ofthe thermocouple. The temperature is regulated by adjusting the air-fuelratio and can vary, depending upon the results to be accomplished, e.g., removal of clogging material from tubing, ignition of oil sands,etc. Once the burning has started the electrical heat input can bediscontinued.

In constructing the bottom hole burner, its length will be a matterdepending upon the conditions to be observed. For instance, the lengthis sufficient to heat the air and oil to combustion initiatingtemperatures. Factors which will affect the length then include theamount of oil and air to be heated, the size of the passage betweenthermowell and tubing 2, the temperature of the subterranean passage,the amount of current passing to the heating coil, etc. It also followsthat the width of the elongated circular passage between the thermowelland tubing 2 can vary and is sufficient to permit the air and oil toform a cornbustible mixture. The width should not be so great that theair and oil cannot be heated even at low ow rates to temperatures toinitiate combustion. Also, the width should not be so small as torequire extremely high pressures for passing combustible fluids throughthe circular passage. For instance, the width is advantageously about 10to 20 thousandths of an inch when tubing 2 has an internal diameter ofone-half inch.

Thus it is seen that my invention provides a compact, eiicient, rapidand inexpensive means for initiating and maintaining combustion insubterranean passages. It also provides simple and adequate means forfollowing at the earths surface temperatures of heating and combustionin the passages.

I claim:

A bottom hole burner comprising a vertically elongated tubing having anopen lower end, a cylindrical thermowell disposed within said tubing andhaving a diameter which permits iiow of combustible fluids between theoutside of the thermowell and the inside of the tubing, said thermowellhaving its lower end projecting just beyond the lower end of the tubing,a thermocouple disposed within and at the lower end of said thermowell,an electrical heating coil disposed around said tubing at its bottom andalong its length suicient to heat the combustible fluids to combustiontemperature, and a protective sheath disposed around said electricalheating coil.

References Cited in the le of this patent UNITED STATES PATENTS1,715,592 Christians June 4, 1929 1,835,400 ingison et al Dec. 8, 19312,484,063 Ackley Oct. 11, 1949 2,506,853 Berg et al May 9, 1950

